Carpet-shampooing devices having counterrotating cup-disk brushes are known in a variety of constructions. For the purposes of this description, a cup-disk brush is a brush constituted by a disk which is rotated and from which an annular array of bristles extend generally downwardly, the cup being an upwardly open central cavity in the brush.
The machine generally comprises, in addition to a housing on which the brushes are journaled for rotation about vertical axes perpendicular to the planes of their disks, a handle extending from the housing and enabling the operator to push the apparatus across the carpet or rug, a motor on or in the housing for driving the brushes in opposite sense so that they do not produce a resultant lateral movement, a receptacle for the shampooing agent and a valve system, generally operated by a trigger or other device on the handle, enabling the shampooing agent to be discharged onto the carpet and brush bristles.
Generally speaking conventional shampooing machines of this type resemble multiple-disk household floor-polishing or waxing machines and can have two, three or even four disk brushes. When two disk brushes are used, they are always driven in opposite senses to counteract the tendency of each brush to swing the machine to one side. In single-brush machines, however, the operator must constantly exert a force to counteract this tendency.
In polishing machines the disk brushes carry the entire weight of the apparatus, i.e., the motor, the housing and the handle, the downward force being applied to the shaft carrying the brush. However, in shampooing apparatus the motor and housing may be supported by wheels although the brush bristles nevertheless engage the carpet and penetrate at least to a limited extent into the pile thereof during the shampooing process.
The housing may comprise a motor-support plate, direction-changing gearing (when the motor shaft lies horizontally) to rotate the brushes about vertical axes, gearing to produce the counterrotation of the two brushes and/or speed-reducing gearing, such as a worm drive, to transform the motor output to the optimum brush speed for the shampooing operation.
The housing may be surrounded by an apron which extends downwardly, although this apron should not reach the floor surface and thereby prevent effective shampooing. The housing may be completed by a protective cover for the motor and transmission elements, bearings and the like.
The handle may either be of a T-construction having opposing hand grips similar to those of a bicycle, or of loop construction. The lower portion of the handle or loop is formed with a hinge which enables the housing to maintain a horizontal position regardless of the manner in which the upper end of the handle is held by the operator.
Electric current supply to the motor is effected by a cable which can run directly to the motor housing or can pass through the handle and extend out of a grip thereof.
The tank, generally carried on the handle structure, customarily has a capacity of about 2 to 4 liters and is provided with a filling opening through which shampoo can be introduced, a vent to allow air into the tank as the shampooing agent drains therefrom and the aforementioned valve mechanism which, by operation of a lever on the handle, communicates the interior of the tank with a tube running between the motor-support plate and the brushes.
Either at this plate or further above the liquid is branched into two passages which open close to the axles of the brushes to permit the shampooing agent to pass downwardly into the rotating cups of the cup-disk brushes. The liquid is cast outwardly by centrifugal force, generally without prefoaming, onto the bristles and the carpet where agitation of the brush bristles against the carpet pile in the presence of the liquid produces the foam necessary for effective cleaning.
Since the shampooing agent is a substance of high wetting capability, it is readily taken up by capillary passages of the carpet material. Consequently, any portion of the shampooing agent which is not immediately converted to foam by agitation of the bristles is no longer available for foaming. Of course, effective foaming can also occur when there is practically complete saturation of the carpet material so that the bristles agitate a wet carpet surface.
The operator opens and closes the valve as he deems necessary for effective shampooing and usually must hold the valve open to saturate the carpeting before he is able to notice the development of the foam. Since the bristles are most effective only along the carpet's upper surface and only lightly engage the latter, a fraction of the shampooing agent absorbed in the carpet is agitated sufficiently to form the foam. Since the operator may not see enough foam he will tend to hold the valve open longer, causing still more soaking of the carpet.
The result is an extremely wet and liquid-permeated carpet, slow progress of the machine thereover and less than effective shampooing. With such earlier apparatus it has not been possible to apply effectively a shampooing foam to the floor with the bristles.
In another type of carpet shampooer, namely, the drum-type, it has been known for some time to foam the shampooing agent before it contacts with the carpet, permitting effective cleaning with minimum soaking; thus the foam is a dilution of the shampooing agent with air and has a higher viscosity than the shampooing liquid and a reduced density, enabling it to be easily spread on the carpet with little tendency to penetrate deeply therein. German published application -- Auslegeschrift -- No. 1,557,240 describes such a drum-type device in which a dried foam is preformed and is massaged into the carpet with mechanical oscillation.
The shampooing agent, even after vacuuming of the dried residues together with the released foam, is found in these systems not to penetrate sufficiently deeply into the pile of the carpet and even where it does manage to penetrate the carpet deeply, cannot readily be removed by vacuuming and hence remains as a dirt-carrying substance. The latter disadvantage also characterizes those shampooing systems where the carpet is soaked and thereafter subjected to vacuuming in the wet state.
The German utility model (Gebrauchsmusterschrift) No. 7412248 describes an accessory which is capable of generating foam by mixing air with the shampooing agent before the latter reaches the carpet. The accessory uses the rotating brushes for the prefabrication of the foam. On the surface of the lower horizontal bottom portion of the cup wall of the brush there are pivoted radial entraining ribs at the hub of the brush which cooperate with nonrotating fixed annular brushes within the brush cup and which have bristles designed to pass into the space between the ribs. As the bristles of the accessory brushes strike the ribs a foam is formed in accordance with the washboard principle. The foam is expelled through lateral passages in the brush cup to the bristle crown of the shampooer brushes and then along these bristles onto the carpet. The shampooing agent is thus not soaked into the carpet but is worked into the latter by the bristle crowns of the shampooer brushes. The advantage of this system is that substantially less shampooing agent is required than with systems in which the carpet is permeated by the foaming agent and a soaking of the carpet is avoided.
It has been found, however, that the last-mentioned prefoaming system is not practical. Firstly, the impact between the nonrotating brush and the ribs increases the already high resistance to brush rotation, putting a significant load upon the motor. Furthermore, the nonrotating brush annulus is subject to rapid deterioration and must either be frequently replaced or operated in an inefficient manner.
Furthermore, when the machine is stopped, the foam-generating brushes may be permanently deformed by the ribs and are thus gradually rendered ineffective.
There has been proposed a variation to the system described above (see German utility model -- Gebrauchsmusterschrift -- No. 7443261). In this construction, instead of ribs, the rotating cup bottom of the cup-disk brush is provided with tooth crowns and in the spaces between the tooth crowns and/or between the outer tooth crowns and the cylindrical periphery of the cup wall, nonrotating fixed impingement baffles are received with clearance. The shampooing agent is introduced at the center of the cup-disk brush and passes through the gaps between the tooth crowns outwardly to spray upon the impingement walls and generate foam. Finally the foam is forced outwardly through openings in the peripheral wall and is supplied to the carpet.
Because of the clearances between the cooperating moving and nonmoving parts the additional friction factors and dangers of the earlier systems are avoided. However, even this system has some significant disadvantages, since experience has shown that it can operate only with sprays having a relative strong throughflow of the shampooing liquid. With low liquid flow rates the shampooing agent forms a film through the gap and does not spray against the impingement walls, thus passing out of the system in an unfoamed state.
A rigid impingement wall system designed to be free from contact or friction when cooperating with the tooth crowns is also expensive because it requires precise positioning and machining of the impingement walls. In spite of a desire to avoid contact between the rotating and nonrotating parts, contact occasionally occurs and when the gaps through which the liquid can pass are minimized, this danger increases. Particularly with relatively slow rotation and low liquid supply rates it is impossible to prevent migration of the liquid film without foaming to the outlet even with the most elaborate of design and fabrication efforts.